With the recent development in the information communication technology, diverse wireless (or radio) communication technologies have also been under development. Among such technologies, Wireless LAN (WLAN) corresponds to a technology allowing wireless access to the Internet in households, companies, or specific service provided areas by using mobile user terminals (or user equipments), such as a Personal Digital Assistant (PDA), a laptop computer, a Portable Multimedia Player (PMP), and so on, based upon a radio frequency technology.
In order to overcome the limitations in the communication rate (or communication speed), which has been noted as a vulnerability in WLAN, in the most recent technology standard, a system that has enhanced network speed and reliability and that has extended the operation range of a wireless network has been applied. For example, IEEE 802.11n supports a High Throughput (HT) having a maximum data processing rate of 540 mbps or more and also adopts the application of a MIMO (Multiple Inputs and Multiple Outputs) technology, which minimizes transmission error, and which uses multiple antennae at both transmitting and receiving units in order to optimize the data rate.
In a MAC (Medium Access Control) layer of an IEEE 802.11 group system, a new standard for supporting fast initial link setup with respect to stations (STAs), which support the IEEE 802.11 group, is being developed as IEEE 802.11ai. In a situation where a significantly large number of users deviate from their initially connected and WLAN coverage and substantially access a new WLAN at the same time, such as during public transportation transfer, an object of the IEEE 802.11ai, for example, is to provide a technology for supporting link setup at a fast rate. Furthermore, the main features of IEEE 802.11ai may be summarized as a security framework, an IP address assignment, fast network discovery, and so on.